The invention relates to communications systems having multiple nodes used in wells.
After a wellbore has been drilled, various completion operations may be performed in the wellbore, in which equipment including packers, valves, flow tubes, and other devices may be set to control fluid production from one or more zones in the well. With advances in technology, sensing and control devices may be placed downhole to monitor and to adjust conditions downhole as needed.
An example system that monitors downhole conditions may include various downhole gauges and sensors that are capable of monitoring temperature, pressure, and flow information. Using a communications link, such as an acoustic data link or a digital telemetry link, data gathered by the gauges and sensors may be sent to the surface to control boxes. The data may then be processed to determine the conditions downhole so that production may be improved and potential reservoir problems may be avoided. In addition to gauges and sensors, other downhole systems may include control devices that may be used to adjust equipment settings downhole.
The communications link between the surface and the downhole equipment is typically a very long link. Conventionally, the link is in the form of one or more electrical wires coupling the downhole equipment to the surface equipment, and the length of the one or more wires may be thousands or tens of thousands of feet long. In addition, the links are associated with transfer characteristics. Consequently, signal attenuation and distortion may occur when the signal is transmitted over a link, which may result in communications errors.
Some communications systems have implemented mechanisms to counteract the distortion effects of cable lines. However, a need continues to exist for improved methods and apparatus for reliable communications between devices coupled to communications lines.